Influence of surface treatment by HCl aqueous solution on electrochemical characteristics of a Mm(Ni–Co–Al–Mn) 4.76 alloy for nickel–metal hydride batteries

Abstract

Surface treatment of a Mm(Ni 0.64Co 0.20Al 0.04Mn 0.12) 4.76 alloy used as negative electrode material was examined to improve the performance of nickel–metal hydride secondary batteries. The surface treatment was conducted by dipping and stirring the alloy into an HCl aqueous solution of pH 1.0 at room temperature. Initial discharge characteristics and charge–discharge cycle performance of the surface-treated alloy were evaluated by an electrochemical half cell and a sealed test cell. The surface structure of the surface-treated alloy was analyzed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) with an energy disperse X-ray spectrometer (EDX). In this paper, the influence of the surface treatment on the charge–discharge characteristics, particularly on the initial discharge characteristics, and surface structure of the alloy are discussed.